In cataract surgery, the natural lens is removed. To refocus the light on the retina and thus restore vision, an intraocular lens assembly can be implanted in place of the natural lens.
Intraocular lens assemblies can be implanted at various locations within the eye, such as within the anterior chamber or within the posterior chamber. Although an intraocular lens assembly is ostensibly of very simple construction, there is a wide variety of problems which has caused substantial study to be done in this field. As a result, a large number of intraocular lens assemblies have been proposed.
An intraocular lens assembly comprises a lens and structure to retain and support the lens within the eye. The retaining and supporting structure may include at least two support members, which are often referred to as loops. Each of the support members typically comprises an elongated strand which is resiliently deformable to facilitate insertion of the assembly to its desired location within the eye. When implanted, the strand resiliently bears against an adjacent surface of the eye to retain and position the lens.
One form of support member comprises a strand having one end affixed to the lens and its other end terminating at a location spaced radially of the lens. Such a construction is shown by way of example in Shearing U.S. Pat. No. 4,159,546. Implantation of an intraocular lens assembly of this kind requires resilient deformation of the free end of the strand radially inwardly toward the lens. If the strand and the lens are not precisely aligned in the same radial plane, the radial inward compression of the strand can act to move the lens axially out of the radial plane to impede the implantation process.
In another form of support member, both ends of the strand are attached to the lens, and a region of the strand intermediate its ends lies radially outwardly of the lens to support the lens in the implanted condition. One such construction is shown in Sheets U.S. Pat. No. 4,328,595. This construction tends to solve the problem of the lens moving axially in response to radial movement of the support member. However, this double-strand patented construction is somewhat difficult to compress radially. In addition, only point or narrow region contact is obtained with the surface of the eye which it engages in the implanted condition, and this increases unit loading on the eye and makes it difficult for the surgeon to rotate the lens assembly within the eye during implantation.
It is also known to provide intraocular lens assemblies which can be supported by hangers or clips rather than by using resilient elements acting against various eye surfaces, such as the posterior bag. One such device is shown in Rainin U.S. Pat. No. 4,203,168 which provides an anchor which extends through the iris. Constructions of this type are quite different from those which utilize the resilience of one or more support members to retain and position the lens assembly and are not suited for use in the capsular bag.